CN1927921B - Lithium ion conducting gel film containing porous polymer framework and preparation method thereof - Google Patents

Abstract

The invention discloses a lithium ion conductive gel film containing a porous polymer skeleton and a preparation method thereof. It has a modified polymer porous membrane skeleton, which is filled with lithium salt, diluent, and crosslinked polyether to carry out crosslinking reaction in the modified polymer porous membrane skeleton. The steps of the preparation method: (1) preparing polypropylene glycol-modified polyvinylidene fluoride or polyethersulfone porous membrane by phase inversion method; (2) mixing carbonate, lithium salt, polyethylene glycol and diisocyanate at 10-20°C Mix to prepare an electrolyte; (3) Soak the porous membrane in the electrolyte for 10-30 minutes at 10-20°C to absorb the electrolyte; (4) Treat the porous membrane that absorbs the salt electrolyte at 60°C for 8-10 minutes Hours for cross-linking and gelation. This method is easy to operate and apply, and the obtained gel film has high strength, stable shape, high loading rate of lithium salt electrolyte, and conductivity between 10 ^-3 and 10 ^-2 S/cm, which is suitable for the integration of diaphragm and electrolyte Polymer lithium ion battery is used.

Description

Lithium-ion conductive gel membrane containing porous polymer skeleton and preparation method thereof

technical field

The invention belongs to the technical field of polymer electrolytes, in particular to a lithium ion conductive gel film containing a porous polymer skeleton and a preparation method thereof.

Background technique

Lithium-ion battery, also known as lithium secondary battery, is a rechargeable secondary power supply with high specific energy, excellent electrical performance, and can be made into various shapes. It is widely used in mobile phones, electric vehicles, notebook computers, Fields that require portable power such as photography/photography. With the continuous growth of demand in related industries, lithium-ion battery materials and technologies are in a stage of rapid development. Improving the safety, energy density and long life of lithium-ion batteries is the development direction of high-performance lithium batteries. In the core materials and technologies of lithium-ion batteries, the type and performance of the electrolyte system between electrodes has a great influence on the battery structure and manufacturing technology, internal resistance of the battery, charge-discharge current density, charge-discharge cycle characteristics, ionic conductivity, electrochemical window, different Leakage and anti-overcharge and discharge safety have a decisive impact, and it is one of the keys and cores of lithium-ion batteries. In the past 20 years, the technology and progress of lithium-ion batteries are almost determined by the electrolyte system. According to different electrolyte systems, the development of lithium-ion battery technology can be roughly divided into three stages of development: liquid lithium-ion batteries, solid-state lithium-ion batteries, and gel lithium-ion batteries.

The liquid lithium-ion battery technology adopts the electrolyte system to prepare a polyethylene single-layer microporous membrane by a thermally induced phase separation method, or a polypropylene single-layer microporous membrane or a polypropylene/polyethylene multilayer by a melt-forming-stretching pore-forming method. The composite microporous membrane is an electrode separator membrane with a pore size of 0.5 μm and a thickness of 20-30 μm. The membrane is filled with a liquid lithium salt electrolyte. Related patents such as US 3801404, US 3558764, US 3843761, US 5691047, etc. This kind of technology using liquid as electrolyte is currently the most widely used technology in lithium battery products, but there are separators made of polyethylene and polypropylene with low porosity, poor affinity for electrolyte, and easy penetration of liquid electrolyte. Leakage and other problems, resulting in adverse results such as large internal resistance, low energy density, fast performance decay, and low safety.

Solid-state lithium-ion battery technology uses a polymer composite film with lithium ion conductivity as the electrolyte between electrodes. The basic principle is to use oxygen complexed lithium ions in polyethylene oxide, and lithium ions in flexible polyethylene oxide Transition lithium ions conduct electricity. A typical preparation method is that polyethylene oxide, lithium salt, and solvent are mixed into a solution, and the solution is formed into a film to evaporate the solvent to obtain a polyethylene oxide composite film containing lithium ions (such as: Feuilade G, J Appl Electrochem, 1795, 63 ; Appetecchi G B, J Electrochem Soc, 2001, A1171; Appetecchi G B, J Electrochem Soc, 2002, A891, etc.). Due to the low strength of polyethylene oxide film, it is also proposed to prepare solid film by blending, grafting or crosslinking polymers such as polymethyl methacrylate, polystyrene, polyacrylonitrile and polyethylene oxide. The method of lithium ion composite membrane (such as: W Wieczorek, Electrochim, 1992,1565; Z Florjanczyk, Polymer, 1991,3422; Z Florjanczyk, Pure Appl.Chem, 1992,853; Y Kato, Solid State Ionics, 2001,155; Fu Yanbao, Power Technology, 2002, 47, etc.). Compared with the electrolyte system in liquid lithium-ion batteries, the main feature of solid-state lithium-ion battery technology is that the polymer electrolyte has the dual functions of electrolyte and diaphragm, from the requirements of small size, light weight, long life, high safety performance, and easy battery shape design It seems that there are obvious advantages, but because the conductivity of the polymer composite membrane is too low (far less than 10 ^-3 S/cm), it cannot meet the requirements of practical application at present.

The gel polymer electrolyte membrane containing lithium ions used in the gel lithium-ion battery is used as the electrolyte material between the electrodes, which is essentially an all-solid-state lithium-ion battery. Compared with the electrolyte membrane for all-solid-state lithium-ion batteries, it is mainly used in Adding a plasticizer or diluent to the membrane makes the electrolyte membrane in a gel state, which reduces the crystallinity of the polymer chain and improves the mobility and conductivity of lithium ions. There are three existing methods for preparing lithium ion gel polymer electrolyte membranes. (1) Blending casting method: Mix polymer, low boiling point solvent, high boiling point diluent/plasticizer and electrolyte into a uniform solution, cast and scrape it on a glass plate, stainless steel or polyester tape to form a liquid film , and then the solvent is completely evaporated to obtain a gel polymer electrolyte membrane. All raw materials in the operation must be strictly dried in advance, and the whole process must be carried out under anaerobic and water-free conditions, and the process conditions are harsh. (2) Mixing-polymerization method: the monomer, initiator, electrolyte, and cross-linking agent are mixed into a solution and injected into the battery, and the polymerization is initiated after sealing. Compared with the casting method, the harshness of the process conditions is reduced, and the gel polymer electrolyte membrane can be directly produced between the electrodes, which is more suitable for the preparation of lithium-ion batteries, but unreacted monomers and initiators are not easy to remove, which will affect the conductivity. and the stability of the gel polymer electrolyte. (3) Membrane-impregnation electrolyte method: the basic process is to mix polymers (mainly poly(vinylidene fluoride-hexafluoropropylene), plasticizers (sometimes also called pore-forming agents), and solvents and then cast them into liquid After the membrane and the solvent are evaporated, a solid membrane is obtained, and then the plasticizer or pore-forming agent is extracted with an extractant to obtain a polymer skeleton with a porous structure, and finally the dried membrane is immersed in a lithium salt electrolyte to adsorb the electrolyte for activation. Since the essence of the method is The solvent of the electrolyte has a swelling effect on the porous skeleton, resulting in gelation in the skeleton and increasing the amount of electrolyte adsorption, but the force between the gel in the pores and the polymer skeleton is very small, and it is basically a free solution. When the internal pressure of the battery increases, the electrolyte will still be released from the polymer matrix.

The polymer system of the lithium ion gel electrolyte membrane prepared by the above three methods has a polyethylene oxide system (such as: Tang Zhiyuan, Polymer Material Science and Engineering, 2003, 48; M Borghini, Electrochim Acta, 1996, 2369 ; Kang, JPower sources, 2003, 432 etc.), PAN system (such as: Y Matsuda, J Power Sources, 2003, 473; DPeramunage, Solid State Ionics, 1994, 79 etc.), PMMA system (such as H J Ryoo, Solid State Electrochem , 1998, 1; A M Stephan, J Power Sources, 1999, 752; D W Kim, J Power Sources, 2000, 78, etc.) and fluorine-containing polymer systems (such as: US Patent 5418091, 1995; US 5658685, 1997; US 5716421, 1998; US5296318 and D Saikia, Phys.Stat.Sol., 2005, (a) 202(2): 309, etc.) and other four categories. Although the conductivity of the gel polymer electrolyte membrane of these systems can reach more than 10 ^-3 S/cm, there are still some problems in the following aspects when used as the electrolyte membrane of lithium batteries: the strength and dimensional stability of the gel polymer electrolyte membrane Generally low, such as the volume of polymethyl methacrylate system continues to shrink significantly over time, not only electrolyte loss, but also may be detached from the electrode; the compatibility of polymers such as polystyrene and polyacrylonitrile with electrode materials Poor, phase separation occurs in the system and the performance of the electrolyte decreases, and the electrochemical window decreases (such as: Kim, J Power Sources, 2001, 102: 41; Wu, Polymer, 2005, 5929, etc.), even if blending, copolymerization, These problems are also difficult to solve by means of inorganic fillers and cross-linking.

The (vinylidene fluoride-hexafluoropropylene) copolymer has good film-forming properties and mechanical strength, and has a high dielectric constant and excellent electrochemical stability. It is more suitable for the use of gel polymer electrolyte membranes. At present, high The research on performance gel polymer electrolyte is mainly based on (vinylidene fluoride-hexafluoropropylene) matrix. Among them, the hexafluoropropylene segment aggregation area is highly elastic, has good swelling property, can absorb more electrolyte, and makes the electrical conductivity reach 10 ^-3 S/cm, and at the same time, the vinylidene fluoride segment aggregation area is in a crystalline state , and endow the gel polymer electrolyte membrane with good mechanical properties (Wu Yuping, Lithium-ion Batteries: Application and Practice, Chemical Industry Press, 2004). Purely from the comprehensive performance of GPE, poly(vinylidene fluoride-hexafluoropropylene) is an ideal gel polymer electrolyte membrane material for lithium batteries, but the expensive price of poly(vinylidene fluoride-hexafluoropropylene) is a limitation The main problem of its large-scale application.

In principle, the conductive mechanism of the gel polymer electrolyte membrane is that the lithium ion coordinates with the electron-donating polar groups (such as nitrogen, oxygen, fluorine, etc. atoms) on the polymer chain. The thermal movement of the molecular chain segment in the high elastic region, lithium ions and polar groups continue to undergo a process of coordination and decoordination, so as to realize the migration of ions, that is, the conduction behavior mainly occurs in the amorphous region, while the crystalline region has a great influence on the conductivity. In order to improve the conductivity, it is necessary to reduce the crystallinity of the polymer; on the other hand, the strength of the highly elastic polymer electrolyte membrane is low, and it is necessary to have a certain degree of crystallization, cross-linking or adding a reinforcing agent to improve the electrolyte membrane. Strength of. Therefore, the essence of the design principles of gel polymer electrolyte membranes for lithium batteries can be summarized as follows: first, to achieve high and stable electrolyte absorption without loss; second, the polymer matrix has sufficient mechanical strength, heat/ It has good chemical stability and does not cause damage to other battery components; third, it is easy to be prepared and applied on a large scale; and fourth, it has low cost of raw materials.

Based on the above analysis, on the basis of sufficient experiments, a lithium-ion conductive gel electrolyte membrane different from the previous composition and structure is proposed, and the preparation of this gel electrolyte membrane and its use in lithium-ion batteries are provided in detail. method.

Contents of the invention

The object of the present invention is to provide a lithium ion conductive gel film containing a porous polymer skeleton and a preparation method thereof. To solve the problems of low electrolyte absorption and retention rate, low conductivity, high cost, and poor strength in the existing lithium-ion conductive gel electrolyte membrane, and promote the development of safe, high-performance, and low-cost lithium-ion battery technology.

The lithium-ion conductive gel membrane containing a porous polymer skeleton has a modified polymer porous membrane skeleton, and the modified polymer porous membrane skeleton is filled with a product obtained by cross-linking a lithium salt, a diluent, and a cross-linked polyether. .

The modified polymer porous membrane skeleton is composed of a main body polymer and a modifier, wherein the weight percentage of the main body polymer is 70-90% based on the total mass of the modified polymer porous membrane skeleton, and the weight percentage of the modifier is 10-90%. 30%, the main polymer is polyvinylidene fluoride or polyethersulfone, and the modifier is dihydroxypolypropylene glycol with a relative number average molecular mass of 3000-4000.

The structure of the modified polymer porous membrane skeleton is: it has continuous pore channels, the pore diameter is 0.2-3.0 μm, the porosity is 60-80%, and the thickness is 15-25 μm.

Based on the total mass of the lithium salt, the diluent and the cross-linked polyether, the mass percentage of the lithium salt is 3-5%, the diluent is 20-30%, and the cross-linked polyether is 65-75%.

The cross-linked polyether is a reaction product of dihydroxypolyethylene glycol and diisocyanate, wherein the mass percentage of dihydroxypolyethylene glycol with a molecular weight of 200-1400 is 85-90%; the mass percentage of diisocyanate is 5-10%.

The lithium salt is lithium hexafluorophosphate or lithium perchlorate, the diluent is diethyl carbonate, dimethyl carbonate or methylethylene carbonate, and the diisocyanate is toluene-2,4-diisocyanate, diphenylmethane diisocyanate or isophorone diisocyanate.

The preparation method of the lithium ion conductive gel film containing porous polymer skeleton comprises the steps:

1) Preparation of dihydroxypolypropylene glycol-modified polyvinylidene fluoride or polyethersulfone porous membrane skeleton by phase inversion method;

2) Mix lithium salt, diluent, dihydroxypolyethylene glycol, and diisocyanate at 10-20°C to prepare an electrolyte solution, wherein the mass percentage of lithium salt is 3-5%, and the mass percentage of diluent is 20-30% , the mass percentage of dihydroxypolyethylene glycol is 55-70%, the molecular weight is 200-1400, the mass percentage of diisocyanate is 3-7%, and the sum of the mass percentages of each component is equal to 100%;

3) Soak the porous membrane skeleton in the above-mentioned electrolyte at 10-20°C for 10-30 minutes to absorb the electrolyte;

4) The porous membrane skeleton with the electrolyte absorbed is treated at 60-80° C. for 8-10 hours to carry out cross-linking and gelation.

The lithium salt is lithium hexafluorophosphate or lithium perchlorate, and the diluent is diethyl carbonate, dimethyl carbonate or methyl vinyl carbonate.

The steps of preparing polyvinylidene fluoride or polyethersulfone porous membrane skeleton modified by dihydroxypolypropylene glycol by phase inversion method are:

1) Mix dihydroxypolypropylene glycol, polyvinylpyrrolidone, water, solvent with polyvinylidene fluoride or polyethersulfone, stir at 70°C for 24 hours, and then stand in vacuum at 30°C for 10 hours to degas to obtain a cast film liquid;

2) In an air environment with a temperature of 10-30°C and a relative humidity of 40-80%, scrape the casting solution at 50-60°C on a stainless steel plate at 40-50°C to form a liquid film with a thickness of 50-150 μm ;

3) Immerse the stainless steel plate with the liquid film in a coagulation bath with a temperature of 30-60°C and stay for 2-10 minutes to solidify and form a film;

The composition and mass percentage of the coagulation bath are as follows: the first component: water: 20-100%, the second component: corresponding to N, N'-dimethylformamide or N, N' used in the casting solution -Dimethylacetamide solvent: 0-80%;

4) Take the cured film out of the coagulation bath, soak and wash in water at 20-40°C for 48 hours, and dry at 60-80°C for 24 hours.

The components of the casting solution and their mass percentages are: dihydroxypolypropylene glycol, 1-3%, molecular weight 3000-4000; polyvinylpyrrolidone, 1-4%, molecular weight 2×10 ³ ～2×10 ⁶ ; water: 2-5%; solvent is N, N'-dimethylformamide or N, N'-dimethylacetamide, 73-86%; polyvinylidene fluoride or polyethersulfone, 10-15 %.

Beneficial effects of the present invention:

The polyvinylidene fluoride or polyethersulfone porous membrane with a porosity as high as 60-80% is used as the skeleton, the electrolyte absorption rate is high, and the lithium ion conductive gel membrane obtained has high conductivity.

In addition, since dihydroxypolypropylene glycol is blended in the polyvinylidene fluoride or polyethersulfone porous membrane as the skeleton, polypropylene glycol can not only inhibit the crystallization of polyvinylidene fluoride or polyethersulfone, but also the diluent in the polyelectrolyte, lithium The salt can interact with the propylene glycol in the porous membrane to properly swell the skeleton, absorb more electrolyte, and further improve the conductivity of the lithium-ion gel membrane.

In addition, the cross-linked polyethylene glycol gel containing lithium salt is filled in the porous framework, so that the leakage of electrolyte solution does not occur, and the safety is improved.

In addition, polypropylene glycol has good compatibility with polyvinylidene fluoride or polyethersulfone, which is beneficial to the stability and strength of the porous skeleton.

In addition, polypropylene glycol has good compatibility and interaction with polyvinylidene fluoride or polyether sulfone. When the porous membrane is prepared by the phase inversion method, a coagulation bath with water as the main component is used, and it can be retained in the porous membrane.

In addition, the hydroxyl group of polypropylene glycol on the surface of the porous skeleton can react with the cross-linking agent in the electrolyte, so that the porous skeleton and the filled cross-linked polyethylene glycol gel can be integrated, and the compatibility and coagulation between the skeleton and the filled gel electrolyte can be improved. The shape stability of the adhesive film.

In addition, filling the cross-linked polyethylene glycol gel containing lithium salt in the porous framework can adopt a higher concentration of lithium salt, which is beneficial to the improvement of the conductivity of the lithium ion gel membrane.

In addition, using polyvinylidene fluoride or polyethersulfone porous membrane as the skeleton, the mechanical strength of the lithium ion gel membrane is improved.

In addition, polyvinylidene fluoride or polyethersulfone porous membrane is used as the skeleton, the porous membrane can be placed between the electrode, and then the electrolyte is injected into the case by vacuum method. It is easy to operate and has low environmental requirements. It is more suitable for Used in the manufacture of lithium-ion batteries.

In addition, the preparation method of polypropylene glycol modified polyvinylidene fluoride or polyethersulfone porous membrane is simple, low in cost and high in efficiency, and can replace expensive poly(vinylidene fluoride-hexafluoropropylene) as a lithium ion battery.

In addition, the hyperbranched polymer is used as the cross-linking agent of polyethylene glycol gel, the electrolyte has low viscosity/good fluidity, and keeps liquid for a long time, which ensures sufficient storage time for subsequent use after the electrolyte is prepared , and make the porous membrane fully absorb the electrolyte more fully and finally improve the conductivity of the gel membrane.

In addition, the polypropylene glycol-modified polyvinylidene fluoride or polyethersulfone porous skeleton has large pore size and good connectivity, and there are polypropylene glycol chains on the surface and the pore wall, which ensures that the electrolyte solution fully wets the skeleton membrane and electrolyte solution The rapid absorption improves the preparation efficiency of the gel film.

Description of drawings

Fig. 1 (a) is the scanning electron micrograph of the upper surface of polyvinylidene fluoride porous skeleton polymer sample in embodiment 1;

Fig. 1 (b) is the scanning electron micrograph of the lower surface of polyvinylidene fluoride porous skeleton polymer sample in embodiment 1;

Fig. 1 (c) is the scanning electron micrograph of sample conductive gel film sample upper surface after crosslinking in embodiment 1;

Fig. 2 (a) is the scanning electron micrograph of the upper surface of polyethersulfone porous skeleton polymer sample in embodiment 4;

Fig. 2 (b) is the scanning electron micrograph of the lower surface of the ethersulfone porous skeleton polymer sample in Example 4;

Fig. 2 (c) is the scanning electron micrograph of the upper surface of the sample conductive gel film after crosslinking in embodiment 4;

Fig. 3 (a) is the scanning electron micrograph of the upper surface of polyvinylidene fluoride porous skeleton polymer sample in embodiment 13;

Fig. 3 (b) is the scanning electron micrograph of the lower surface of polyvinylidene fluoride porous skeleton polymer sample in embodiment 13;

Fig. 3(c) is a scanning electron micrograph of the upper surface of the sample conductive gel film sample after crosslinking in Example 13.

Detailed ways

The lithium-ion conductive gel membrane with a conductivity of 10 ^-3 -10 ^-2 S/cm and a porous polymer skeleton proposed in the present invention is, in principle, modified by polyvinylidene fluoride or polyethersulfone in polypropylene glycol. The membrane pores of the porous membrane (that is, the porous skeleton of the gel membrane) are filled with cross-linked polyethylene glycol gel containing lithium ions, and the membrane skeleton is swollen and absorbed by the electrolyte. The preparation process of the gel film and the application method in the production of lithium-ion batteries include four stages, namely: preparation of the porous film, preparation of the electrolyte, absorption of the electrolyte by the porous film and gelation, wherein the gel The application of gel film in the manufacture of lithium-ion batteries is the improvement and development of the method for preparing self-supporting gel film.

1. Preparation of Porous Membrane Skeleton

The solution phase inversion method is used to prepare porous membranes, and the modification of polyvinylidene fluoride and polyethersulfone is realized by adding polypropylene glycol in the casting solution. The preparation method includes the following steps in sequence: (1) preparing the casting solution: adding dihydroxy Polypropylene glycol, polyvinylpyrrolidone, water, solvent and polyvinylidene fluoride or polyether sulfone are mixed and dissolved, and degassed to obtain a casting solution; (2) Scraping liquid film: scrape the casting solution on a stainless steel plate or steel strip to form Liquid film; (3) curing into film: immerse the stainless steel plate with liquid film in a coagulation bath to solidify into film; (4) cleaning and drying.

A porous membrane suitable for using gel membrane as a skeleton needs to have continuous microporous channels, symmetrical structure, high porosity on the membrane surface, pore diameter between 0.2-3.0μm, porosity between 60-80%, and thickness between 15 Between -25μm. In order to obtain a porous membrane with the above structure and meet the requirements of the gel membrane, it is necessary to adjust the formulation of the casting solution, the temperature of the scraping membrane, the composition and temperature of the coagulation bath when solidifying and forming a membrane, and other parameters. The principle of adjusting the membrane structure is to increase the content of polyvinylpyrrolidone in the casting solution, reduce the concentration of polyvinylidene fluoride or polyethersulfone in the casting solution, increase the temperature of the coagulation bath, or increase the content of solvent in the coagulation bath, etc. The method is to prepare a porous skeleton membrane with large pore size and high porosity, and vice versa; the thickness of the porous membrane is controlled by adjusting the thickness of the scraped liquid membrane. When the thickness of the liquid membrane is large, the thickness of the porous membrane is large. The optimal conditions for preparing porous membranes with corresponding structures are as follows:

The components and mass percentages of the casting solution are: dihydroxypolypropylene glycol with a molecular weight of 3400, 2-2.5%; polyvinylpyrrolidone with a number-average relative molecular weight of 1×10 ³ , 2-3%; -N , any one of N'-dimethylformamide or N,N'-dimethylacetamide, 76-82%; water: 3-4%; polyvinylidene fluoride or polyethersulfone: 11-13 %.

Scratch film conditions: Ambient temperature: 20-25°C. The relative humidity of the air is: 60-80%, and the temperature of the casting solution: 50-60°C. Stainless steel plate temperature: 40-50℃, liquid film thickness 50-100μm.

Curing conditions: coagulation bath composition and mass percentage: water: 30-80%, corresponding to N, N'-dimethylformamide or N, N'-dimethylacetamide solvent in the casting solution Any one: 20-70%; the temperature of the coagulation bath is 40-50°C.

In addition, in order to change the water to fully remove the polyvinylpyrrolidone in the porous membrane during the cleaning of the membrane, it is necessary to fully remove the water in the membrane when drying the membrane to avoid the impact of the water contained in the porous membrane on the performance of the final lithium ion gel membrane.

2. Preparation of self-supporting Li-ion conductive gel membrane

Starting from polypropylene glycol-modified polyvinylidene fluoride or polyethersulfone porous membranes, the preparation of self-supporting lithium-ion conductive gel membranes involves three steps. (1) Mix dilute lithium salt, release agent, dihydroxypolyethylene glycol, and diisocyanate below 20°C and stir evenly to make an electrolyte; (2) Soak the porous membrane in the electrolyte at 10-20°C for 10 - 30 minutes to absorb the electrolyte; (3) Treat the porous membrane absorbing the salt electrolyte at 60° C. for 8-10 hours for cross-linking and gelation.

The composition of the electrolyte has an important influence on the subsequent electrolyte absorption, gelation reaction, conductivity, stability and mechanical properties of the gel film. The composition and mass percentage of each component in the optimized formula of electrolyte are:

Lithium salt: any one of lithium hexafluorophosphate or lithium perchlorate, 3-5%;

Diluent: diethyl carbonate, dimethyl carbonate or vinyl methyl carbonate, 20-30%;

Dihydroxypolyethylene glycol: molecular weight 600-1000: 55-70%;

Diisocyanate: toluene-2,4-diisocyanate (TDI), diphenylmethane diisocyanate (MDI) or isophorone diisocyanate (IPDI): 4-6%.

Equimolar ratio of OH to NCO

In addition, in order to ensure the stability of the electrolyte, the configuration and storage of the electrolyte need to be carried out at a lower temperature to prevent too fast cross-linking and gelation; Absorption and swelling, need to use 20-30% diluent, if the content of diluent is too high, the problem of electrolyte leakage will easily occur; in order to obtain the conductivity of the final gel film, it can be ensured that the electrolyte is homogeneous Increase the concentration of lithium salt; in order to prevent the adverse effects of water vapor and oxygen in the air, it is necessary to prepare the gel film, compound with the electrode, and seal the package in an anhydrous and oxygen-free environment.

The following examples describe the present invention in more detail, but the examples do not constitute a limitation to the present invention. The properties described in the patent are determined by the following methods.

(1) Weight average molecular weight (Mw): Measured by GPC based on the molecular weight of polystyrene.

GPC instrument: WATERS high performance liquid chromatography column: GMHXL

Solvent: N,N-Dimethylacetamide Temperature: 25°C

(2) Extraction efficiency

At room temperature, a polymer film with a certain mass (m ₁ ) and size was extracted in the extractant for 24 hours, and weighed as (m ₂ ) after natural drying. The extraction efficiency was calculated by the following formula:

(3) Porosity

Densitometry measurement. After the microporous membrane is dried, cut out a membrane of a certain size, measure its length, width and thickness, weigh the mass, and calculate the density (ρ _m ) of the membrane. The density (ρ _p ) of the polymeric material was 1.77 gcm ⁻³ . The porosity is calculated according to the following formula:

(4) Liquid absorption rate

At room temperature, soak a polymer membrane with a certain mass (m ₁ ) and size in the electrolyte solution for 2 hours, remove the excess electrolyte solution on the surface of the membrane between two pieces of filter paper after taking it out, weigh it as m ₃ , and calculate it according to the following formula Absorption rate:

(5) Determination of electrical conductivity

The conductivity of the polymer electrolyte membrane was measured by the AC impedance method. The polymer electrolyte membrane was sandwiched between two stainless steel electrodes. The Solartron SI1287 electrochemical interface instrument combined with the SI1255B frequency response instrument was used to test the HP2192a analyzer at 25°C. The following formula calculates poly $\mathrm{\σ}=\frac{d}{R_{b}A}$ Conductivity of the membrane:

(4)

Among them, σ is the ionic conductivity (S/cm), d is the thickness of the electrolyte membrane (cm), R _b is the impedance of the electrolyte membrane (Ω), and A is the contact area between the electrolyte membrane and the electrode (cm ^-2 ).

(6) Time stability of conductivity

Place the polymer electrolyte membrane for 16 days, and then test the conductivity according to (7) method.

Main raw materials used in the examples: PVDF: Shanghai 3F, FR904; polyethersulfone: Changchun Jida High-tech Materials Co., Ltd.; N, N-dimethylformamide (DMF): Shanghai Jingwei Chemical Co., Ltd.; N, N-di Methylacetamide (DMAc): Shanghai Jingwei Chemical Co., Ltd.; diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate: Zhangjiagang Guotai Huarong New Material Co., Ltd.; dihydroxypolypropylene glycol, Aldrich; acetone: Shanghai Chemical Reagents General plant; lithium hexafluorophosphate, lithium perchlorate, Shanghai Chemical Reagent Co., Ltd.; Shanghai Chemical Reagent General Factory; toluene-2,4-diisocyanate, diphenylmethane diisocyanate or isophorone diisocyanate (IPDI) Shanghai chemical reagent general Factory; polyvinylpyrrolidone, Sinopharm Shanghai Chemical Reagent Co., Ltd.

The following are the examples of the preparation method of the lithium ion conductive gel membrane containing the porous polymer skeleton, and the implementation conditions of the examples are listed in the list, and the implementation steps of all the examples are the same as the aforementioned implementation steps.

Example 1: The various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 1.

Table 1

Example 2: The various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 2.

Table 2

Example 3: The various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 3.

table 3

Example 4: The various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 4.

Table 4

Example 5: The various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 5.

table 5

Example 6: The various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 6.

Table 6

Example 7: The various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 7.

Table 7

Example 8: The various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 8.

Table 8

Example 9: The various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 9.

Table 9

Example 10: Various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 10.

Table 10

Example 11: Various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 11.

Table 11

Example 12: Various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 12.

Table 12

Example 13: Various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 13.

Table 13

Example 14: Various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 14.

Table 14

Example 15: Various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 15.

Table 15

Example 16: Various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 16.

Table 16

Example 17: Various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 17.

Table 17

Example 18: Various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 18.

Table 18

Example 19: Various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 19.

Table 19

Example 20: Various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 20.

Table 20

Example 21: Various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 21.

Table 21

Example 22: Various implementation conditions and the structure and performance of the obtained lithium ion conductive gel membrane are shown in Table 22.

Table 22

Finally, it should also be noted that what is listed above are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and many variations are possible. All deformations that can be directly derived or associated by those skilled in the art from the content disclosed in the present invention should be considered as the protection scope of the present invention.

Claims (6)

1. A lithium ion conductive gel membrane containing a porous polymer skeleton is characterized in that it has a modified polymer porous membrane skeleton, and is filled with lithium salt, diluent, cross-linked polymer in the modified polymer porous membrane skeleton. The product obtained by carrying out the crosslinking reaction of ether, the modified polymer porous membrane skeleton is composed of a main polymer and a modifier, wherein the mass percentage of the main polymer is 70-90% based on the total mass of the modified polymer porous membrane skeleton, The mass percentage of the modifier is 10-30%, the main polymer is polyvinylidene fluoride or polyethersulfone, the modifier is dihydroxypolypropylene glycol with a relative number average molecular weight of 3000-4000, and the structure of the polymer porous membrane skeleton is modified It has a continuous pore channel with a pore size of 0.2-3.0 μm, a porosity of 60-80%, and a thickness of 15-25 μm. The cross-linked polyether is the product of the reaction between dihydroxypolyethylene glycol and diisocyanate, and the dihydroxypolyethylene glycol with a molecular weight of 200-1400 The mass percentage of ethylene glycol is 85-90%, the mass percentage of diisocyanate is 5-10%, and the sum of the content of dihydroxypolyethylene glycol and diisocyanate is equal to 100%. 2. The lithium ion conductive gel film containing a porous polymer skeleton according to claim 1, characterized in that the lithium salt mass percentage is 3-5% based on the total mass of lithium salt, diluent and cross-linked polyether , The diluent is 20-30%, and the cross-linked polyether is 65-75%. 3. the lithium ion conductive gel film containing porous polymer skeleton according to claim 1, is characterized in that described lithium salt is lithium hexafluorophosphate or lithium perchlorate, and diluent is diethyl carbonate, dimethyl carbonate or Vinyl methyl carbonate; the diisocyanate is toluene-2,4-diisocyanate, diphenylmethane diisocyanate or isophorone diisocyanate. 4. a preparation method containing the lithium ion conductive gel membrane of porous polymer skeleton as claimed in claim 1, is characterized in that it comprises the steps: 1) Preparation of dihydroxypolypropylene glycol-modified polyvinylidene fluoride or polyethersulfone porous membrane skeleton by phase inversion method; 2) Mix lithium salt, diluent, dihydroxypolyethylene glycol, and diisocyanate at 10-20°C to prepare an electrolyte solution, wherein the mass percentage of lithium salt is 3-5%, and the mass percentage of diluent is 20-30% , the mass percentage of dihydroxypolyethylene glycol is 55-70%, the molecular weight is 200-1400, the mass percentage of diisocyanate is 3-7%, and the sum of the mass percentages of each component is equal to 100%; 3) Soak the porous membrane skeleton prepared in step 1) in the above-mentioned electrolyte solution at 10-20°C for 10-30 minutes to absorb the electrolyte solution; 4) Carrying out the cross-linking gelation reaction at 60-80° C. for 8-10 hours on the porous membrane skeleton adsorbed with the electrolyte; The steps of preparing the polyvinylidene fluoride or polyethersulfone porous membrane skeleton modified by dihydroxypolypropylene glycol by the phase inversion method are: 1) Mix dihydroxypolypropylene glycol, polyvinylpyrrolidone, water, solvent with polyvinylidene fluoride or polyethersulfone, stir at 70°C for 24 hours, then stand in vacuum at 30°C for 10 hours to degas to obtain cast film Liquid, wherein the solvent is N, N-dimethylformamide or N, N-dimethylacetamide; 2) In an air environment with a temperature of 10-30°C and a relative humidity of 40-80%, scrape the casting solution at 50-60°C on a stainless steel plate at 40-50°C to form a liquid film with a thickness of 50-150 μm ; 3) Immerse the stainless steel plate with the liquid film in a coagulation bath with a temperature of 30-60°C and stay for 2-10 minutes to solidify and form a film; In terms of the total mass of the coagulation bath: the first component: water is 20-100%, the second component: corresponding to N, N'-dimethylformamide or N, N'-dimethylformamide in step 1) Acetamide solvent is 0-80%; 4) Take the cured film out of the coagulation bath, soak and wash in water at 20-40°C for 48 hours, and dry at 60-80°C for 24 hours. 5. the preparation method of the lithium ion conductive gel film that contains porous polymer skeleton according to claim 4 is characterized in that described lithium salt is lithium hexafluorophosphate or lithium perchlorate, and diluent is diethyl carbonate, biscarbonate Methyl ester or vinyl methyl carbonate. 6. the preparation method of the lithium ion conductive gel membrane that contains porous polymer skeleton according to claim 4, it is characterized in that each component of described casting film liquid and its mass percentage content are: with described casting film Dihydroxypolypropylene glycol 1-3% by total liquid mass, relative number average molecular weight 3000-4000; polyvinylpyrrolidone 1-4%, molecular weight 2×10 ³ -2×10 ⁶ , water: 2-5%; solvent N, N'-dimethylformamide or N, N'-dimethylacetamide, 73-86%; polyvinylidene fluoride or polyethersulfone, 10-15%.

Images